In a large-sized rotary machine such as a turbine and a generator, a tilting-pad bearing device is used to support a rotation shaft stably. A tilting-pad bearing device is a kind of slide bearings, and includes a plurality of pivotable bearing pads (tilting pads) disposed around the rotation shaft inside a bearing housing. The bearing pads are pivotably supported by pivots disposed inside the bearing housing. When the rotation shaft rotates, lubricant oil is introduced into a gap between the outer circumferential surface of the rotation shaft and the bearing surface of the bearing pads to form an oil film of a wedge shape between the above surfaces, and thereby the tilting-pad bearing device supports the rotation shaft. For instance, Patent Document 1 discloses such a tilting-pad bearing device.
In such a tilting-pad bearing device, it is necessary to eliminate contact between the outer circumferential surface of the rotation shaft and the bearing surface of the tilting pad at the beginning of rotation or at low-speed rotation when an adequate load capability cannot be obtained from the wedge effect of the oil film, so as to prevent galling of the bearing surface. In this regard, a mechanism called a jacking oil pump (JOP mechanism) may be employed. For instance, in the JOP mechanism described in Patent Document 2, an oil-supply inlet is disposed on the bearing surface of the tilting pad, and high-pressure lubricant oil is supplied to the oil-supply inlet from a pump via an oil-supply channel to form an oil film on the bearing surface so that the rotation shaft is levitated by the oil film. Normally, oil grooves are formed on the bearing surface to distribute the lubricant oil over a broad region.